For what it’s worth, I had the same issue with both the Amazon FireSticks and Amazon Fire TV Cube devices. I have 30K albums in my Plex Music library and have no problems playing back files at 5.1, 7.1 or 7.2 file formats on the PS4, PS5 or AppleTV devices. It seems as though your issues are isolated to the Android devices that you are seemingly unwilling to migrate from. The limitation that you are describing has nothing to do with Plex.
